I want to be excited but I'm just super skeptical because of the way the source article is written. It doesn't contain a direct quote from Al saying "Sleep is working on new music" or something to that effect, it's the author's own words- an author that isn't a guaranteed fan of Sleep given what the site looks like.

I'm gonna not get my hopes up and pin this as an honest mistake on the author's part. Al may have said something like "I'm working on new music with my bands" and meant OM and his solo record and the author probably took that to mean a new Sleep album as well. If they are indeed working on a new album though...